Railroad Archives Online
- CollectionD0063 - Walter W. Ainsworth Collection
- Series007 - Spokane, Portland, and Seattle Railway
- Subseries Level 1008 - Ephemera
- ItemWWASPSL9-013 - Spokane, Portland, and Seattle (SP&S) Advertising Postcard at Seaside, Oregon, undated
- ItemWWASPSL9-015 - Spokane, Portland, and Seattle (SP&S) Advertising Postcard at Seaside, Oregon, undated